Role of duplex Doppler and power Doppler sonography in transplanted kidneys with acute renal parenchymal dysfunction

Predictive performance of renal resistive index, semiquantitative power Doppler ultrasound score and renal venous Doppler waveform pattern for acute kidney injury in critically ill patients and prediction model establishment: a prospective observational study

BACKGROUND

This study aimed to explore the performance of renal resistive index (RRI), semiquantitative power Doppler ultrasound (PDU) score and renal venous Doppler waveform (RVDW) pattern in predicting acute kidney injury (AKI) in critically ill patients and establish prediction models.

METHODS

This prospective observational study included 234 critically ill patients. Renal ultrasound was measured within 24 h after intensive care unit admission. The main outcome was the highest AKI stage within 5 days after admission according to the Kidney Disease Improving Global Outcomes criteria.

RESULTS

Patients in the AKI stage 3 group had significantly higher RRI, RVDW pattern and lower PDU score (p < 0.05). Only lactate, urine volume, serum creatinine (SCr) on admission, PDU score and RVDW pattern were statistically significant predictors (p < 0.05). Model 1 based on these five variables (area under the curve [AUC] = 0.938, 95% confidence interval [CI] 0.899-0.965, p < 0.05) showed the best performance in predicting AKI stage 3, and difference in AUC between it and the clinical model including lactate, urine volume and SCr (AUC = 0.901, 95% CI 0.855-0.936, p < 0.05) was statistically significant (z statistic = 2.224, p = 0.0261). The optimal cut-off point for a nomogram based on Model 1 was ≤127.67 (sensitivity: 95.8%, specificity: 82.3%, Youden's index: 0.781).

CONCLUSIONS

The nomogram model including SCr, urine volume, lactate, PDU score and RVDW pattern upon admission exhibited a significantly stronger capability for AKI stage 3 than each single indicator and clinical model including SCr, urine volume and lactate.

Three-dimensional imaging of living transplanted kidney vasculature by 3D color Doppler ultrasonography

Background: It is of clinical importance to display the vasculature of transplanted kidney in three-dimensional (3D) and in non-invasive way. 3D color Doppler ultrasonographic imaging (3D-CDUI) is a non-invasive technique to display the 3D vasculature of living organs. Objective: Probe into characteristics of 3D vasculature of living transplanted kidney by 3D-CDUI, and evaluate the clinical value of 3D-CDUI on monitoring complications after operation of renal transplant. Methods: Nine patients who received allogeneic transplantation of kidney were monitored with 3D-CDUI. The instruments used included ACUSON Sequoia 512 and TomTec computer station of 3D-CDUI. Using magnetic positioning free-hand scanning, the 3D reconstruction and display of renal tissue structure and blood flow were performed off-line. Results: All patients underwent 3D-CDUI examinations without any side effect or complication. When acute rejection occurred, the 3D distribution change of renal blood flow signal could be observed clearly. During treatment of acute necrosis of renal tubules, changes of renal blood flow signal in 3D color Doppler images could be detected earlier compared with 2D color Doppler images. The position of embolized vassels could be diagnosed accurately by 3D-CDUI. Conclusion: The 3D-CDUI was helpful to improve diagnosis level of ultrasonography by monitoring complications after renal transplantation.

The Serial Duplex Index Improves Differential Diagnosis of Acute Renal Transplant Dysfunction

OBJECTIVES

Renal duplex sonography represents a standard noninvasive diagnostic procedure to demonstrate morphologic changes in acute kidney transplant dysfunction. We investigated whether a newly developed serial duplex index (SDI) can differentiate between acute cellular rejection and acute vascular rejection more effectively than the established Doppler parameters of the resistive index (RI) and pulsatility index (PI) in recently transplanted patients.

METHODS

Serial duplex scans of patients with histologically proven acute tubular necrosis (n = 25), acute cellular rejection (n = 28), acute vascular rejection (n = 18), and normal graft function (n = 50, partially protocol biopsied) were retrospectively analyzed. For each patient, the RI, PI, and cortex-pelvis proportion (CPP) were included from the day of biopsy (t0) and 3 to 7 days before biopsy (t-1). The sequential CPP ratio (CPP_t0 /CPP_t-1 ), RI ratio (RI_t0 /RI_t-1 ), and PI ratio (PI_t0 /Pi_t-1 ) were determined. The SDI was calculated as: RI ratio × PI ratio/CPP ratio. The diagnostic accuracy of the SDI was compared with that of the RI and PI ratios.

RESULTS

Selected groups were statistically comparable in all routinely determined transplant parameters. The SDI was significantly different between patients with normal graft function, acute cellular rejection, and acute vascular rejection (P < .01, analysis of variance on ranks), whereas the RI and PI ratios were only significantly different between patients with normal graft function and acute vascular rejection (P < .05, analysis of variance on ranks). The indices' ranges were defined by the 95% confidence intervals between the allograft functions.

CONCLUSIONS

The developed SDI was able to detect acute renal transplant rejection with greater sensitivity and specificity than the RI and PI ratios. Since the SDI distinguishes between acute tubular necrosis, acute cellular rejection, and acute vascular rejection, it might be a supportive tool to indicate renal biopsy.

Role of color Doppler ultrasound in the evaluation of renal transplantation from living donors

PURPOSE

The aim of this study was to evaluate the same kidney before and after transplantation to assess the ability of the allograft to restore blood flow, time required to achieve functional recovery after surgery and the possibility of differentiating normal from pathological allografts using color Doppler ultrasound (CDUS) flow indices: resistive index (RI)/renal cortical ratio (RCR) and scintigraphy.

MATERIALS AND METHODS

79 living donors and 79 recipients. Donors underwent renal CDUS and scintigraphy. CDUS was repeated on the allograft 24 h, 3, 15 and 30 days after transplantation, and scintigraphy 3-5 days after transplantation. Recipients were divided into two groups on the basis of clinical and biochemical values: (A) well-functioning allografts and (B) acute pathology. Results of CDUS, RI and RCI were compared to results of scintigraphy, biochemical values and biopsy.

RESULTS

Group (A) n = 60 (76 %), group (B) n = 19 (24 %); RI sensitivity was 93 %, specificity 83 %. In group (A) positive predictive value (PPV) was 94 % and in group (B) 90 %. RCR using receiver operating characteristic curve analysis yielded sensitivity 100 % and specificity 98.3 %. Scintigraphy mean values of glomerular filtration ratio and T max before transplantation were in group (A): 50.32 ml/min and 4.87 min; after transplantation 46.88 ml/min and 4.96 min; in group (B): 48.68 ml/min and 4.63 min, after transplantation 27.89 ml/min and 10.53 min, respectively. Pearson's correlation coefficient between preoperative and postoperative results of scintigraphy was significant in group (A) (glomerular filtration ratio = 0.85, T max = 0.70) and not significant in group (B) (glomerular filtration ratio = 0.40, T max = 0.08).

CONCLUSION

This study shows that CDUS, RI and RCR are useful in postoperative evaluation of transplanted kidneys as these parameters can, after only 24 h, confirm the good condition of the allograft despite still excessive blood parameter values.

Magnetic resonance imaging in the complications of kidney transplantation

Kidney transplantation is currently the treatment of choice in most patients with end-stage chronic renal failure owing to the excellent results in terms of both graft and patient survival. However, surgical complications are still very frequent. Although urological (stricture, urinary fistulas, vesico-ureteral reflux) and lymphatic complications (lymphocoele) have a high incidence, they only rarely lead to graft loss. By contrast, vascular complications (stenosis, arterial and venous thrombosis, arterio-venous fistulas, pseudoaneurysms) are relatively rare, but potentially serious and may affect graft survival. Finally, medical complications such as acute tubular necrosis (ATN), rejection and de novo neoplasms may also arise in kidney transplantation. The purpose of this pictorial review is to illustrate the increasingly significant contribution of magnetic resonance angiography (MRA) in the management of complications of kidney transplantation, and emphasise how this method should now be considered a mandatory step in the diagnostic workup of selected cases. Moreover, the application and role in this setting of new magnetic resonance imaging (MRI) techniques, such as diffusion-weighted and blood oxygen level-dependent (BOLD) MRI, are also discussed.

Parameters of Doppler ultrasound at five days posttransplantation as predictors of histology and renal function at one year

INTRODUCTION

In our center, a Doppler ultrasound (DU) is performed at 5 days after transplantation. The normal upper limit of flow velocity (FV) in the renal artery is 200-250 cm/s. The resistance index (RI) is considered elevated when >0.8. Elevation of the RI can be shown in all the forms of graft dysfunction.

OBJECTIVE

The objective of this study was to evaluate the capacity of the DU to predict the prognosis of graft function and histological damage at 1 year.

METHODS

We examined a retrospective cohort of patients undergoing renal transplantation between January 2004 and May 2007. The renal function was evaluated with serum creatinine measurements and glomerular filtration rate (GFR) estimates by the quadratic Modification of Diet in Renal Disease study equation. The biopsy specimen was evaluated according to the Banff 1997 classification.

RESULTS

The overall average age was 35 years, and 58% of the subjects were men. Eight cases (25.8%) showed abnormal DU. The Delta among those with normal DU was -0.94 versus 0.27 +/- 0.39 with abnormal DU (P < .005). There was no significance as far as the biopsy at 1 year.

CONCLUSIONS

Renal DU allows physicians to suspect complications at the first posttransplantation year. It shows a tendency to elevated blood pressure, as well as increased deterioration of renal function over the first year.

Renal vascular imaging: ultrasound and other modalities

Sonographic evaluation of the genitourinary system is a fast, safe, and effective means to detect renal disease. In conjunction with other modalities, Doppler can depict a variety of abnormalities. However, optimization of Doppler techniques and a solid understanding of Doppler threshold criteria are critical for success, whether in the native or transplanted kidney.

Avaliação da perfusão renal pelo Power Doppler em pacientes transplantados renais

OBJETIVOS: O objetivo deste estudo é testar a aplicabilidade do estudo ultra-sonográfico com Power Doppler na identificação das alterações da perfusão dos rins transplantados e sua correlação com a reserva funcional renal e microalbuminúria antes e após a infusão de solução de aminoácidos intravenosos. MÉTODOS: Vinte e três pacientes transplantados renais foram avaliados pelo Power Doppler antes (fase basal), após 120 minutos (fase 1) e após 240 minutos (fase 2) da infusão intravenosa de aminoácidos. Concomitantemente, foram realizadas, nas três fases, dosagem de creatinina, avaliação do índice de filtração glomerular, da reserva funcional renal e de microalbuminúria. RESULTADOS: De acordo com os padrões de perfusão na fase basal pelo Power Doppler, descritos por Hoyer et al. em 1999, os pacientes foram divididos em três grupos: 12 pacientes com escore I, seis com escore II e cinco com escore III de perfusão renal. Nos enxertos renais com excelente perfusão renal (escore I), observou-se variação significativa das variáveis estudadas, tanto na fase 1 como na 2 (P CONCLUSÕES: Os achados sugerem que os transplantes com escore I de perfusão apresentam reserva funcional renal quando submetidos a estímulo com aminoácidos. No entanto, com a progressiva diminuição no grau de perfusão renal pelo Power Doppler, observa-se perda da capacidade dos rins transplantados em aumentar o índice de filtração glomerular como resposta a estímulos externos, com seqüente ausência de reserva funcional renal. A partir deste estudo, será possível criar novos horizontes para o entendimento da evolução dinâmica do processo de perda da função renal nos transplantados renais.